From 1a072a3a013976a178e0068be021e23b9a0ed59f Mon Sep 17 00:00:00 2001
From: David Conrad <lessen42@gmail.com>
Date: Thu, 20 Aug 2009 20:44:09 -0700
Subject: [PATCH] Fix unaligned accesses in bitstream writer Fixes x264 on CPUs
 with no unaligned access support (e.g. SPARC). Improves performance
 marginally on CPUs with penalties for unaligned stores (e.g. some x86).

---
 common/bs.h       | 26 +++++++++-----------------
 encoder/cavlc.c   |  4 ++++
 encoder/encoder.c |  2 ++
 3 files changed, 15 insertions(+), 17 deletions(-)

diff --git a/common/bs.h b/common/bs.h
index 68b9f5e35..0c009921a 100644
--- a/common/bs.h
+++ b/common/bs.h
@@ -73,21 +73,22 @@ extern vlc_large_t x264_level_token[7][LEVEL_TABLE_SIZE];
 
 static inline void bs_init( bs_t *s, void *p_data, int i_data )
 {
-    int offset = ((intptr_t)p_data & (WORD_SIZE-1));
+    int offset = ((intptr_t)p_data & 3);
     s->p       = s->p_start = (uint8_t*)p_data - offset;
     s->p_end   = (uint8_t*)p_data + i_data;
-    s->i_left  = offset ? 8*offset : (WORD_SIZE*8);
-    s->cur_bits = endian_fix( *(intptr_t*)s->p );
+    s->i_left  = (WORD_SIZE - offset)*8;
+    s->cur_bits = endian_fix32(*(uint32_t *)(s->p));
+    s->cur_bits >>= (4-offset)*8;
 }
 static inline int bs_pos( bs_t *s )
 {
     return( 8 * (s->p - s->p_start) + (WORD_SIZE*8) - s->i_left );
 }
 
-/* Write the rest of cur_bits to the bitstream; results in a bitstream no longer 32/64-bit aligned. */
+/* Write the rest of cur_bits to the bitstream; results in a bitstream no longer 32-bit aligned. */
 static inline void bs_flush( bs_t *s )
 {
-    *(intptr_t*)s->p = endian_fix( s->cur_bits << s->i_left );
+    *(uint32_t*)s->p = endian_fix32( s->cur_bits << (s->i_left&31) );
     s->p += WORD_SIZE - s->i_left / 8;
     s->i_left = WORD_SIZE*8;
 }
@@ -151,21 +152,12 @@ static inline void bs_write1( bs_t *s, uint32_t i_bit )
 
 static inline void bs_align_0( bs_t *s )
 {
-    if( s->i_left&7 )
-    {
-        s->cur_bits <<= s->i_left&7;
-        s->i_left &= ~7;
-    }
+    bs_write( s, s->i_left&7, 0 );
     bs_flush( s );
 }
 static inline void bs_align_1( bs_t *s )
 {
-    if( s->i_left&7 )
-    {
-        s->cur_bits <<= s->i_left&7;
-        s->cur_bits |= (1 << (s->i_left&7)) - 1;
-        s->i_left &= ~7;
-    }
+    bs_write( s, s->i_left&7, (1 << (s->i_left&7)) - 1 );
     bs_flush( s );
 }
 
@@ -245,7 +237,7 @@ static inline void bs_write_te( bs_t *s, int x, int val )
 static inline void bs_rbsp_trailing( bs_t *s )
 {
     bs_write1( s, 1 );
-    bs_flush( s );
+    bs_write( s, s->i_left&7, 0  );
 }
 
 static inline int bs_size_ue( unsigned int val )
diff --git a/encoder/cavlc.c b/encoder/cavlc.c
index 89bf07d73..0d88bfc6c 100644
--- a/encoder/cavlc.c
+++ b/encoder/cavlc.c
@@ -298,6 +298,7 @@ void x264_macroblock_write_cavlc( x264_t *h, bs_t *s )
 #if !RDO_SKIP_BS
     if( i_mb_type == I_PCM )
     {
+        uint8_t *p_start = s->p_start;
         bs_write_ue( s, i_mb_i_offset + 25 );
         i_mb_pos_tex = bs_pos( s );
         h->stat.frame.i_mv_bits += i_mb_pos_tex - i_mb_pos_start;
@@ -313,6 +314,9 @@ void x264_macroblock_write_cavlc( x264_t *h, bs_t *s )
             memcpy( s->p + i*8, h->mb.pic.p_fenc[2] + i*FENC_STRIDE, 8 );
         s->p += 64;
 
+        bs_init( s, s->p, s->p_end - s->p );
+        s->p_start = p_start;
+
         /* if PCM is chosen, we need to store reconstructed frame data */
         h->mc.copy[PIXEL_16x16]( h->mb.pic.p_fdec[0], FDEC_STRIDE, h->mb.pic.p_fenc[0], FENC_STRIDE, 16 );
         h->mc.copy[PIXEL_8x8]  ( h->mb.pic.p_fdec[1], FDEC_STRIDE, h->mb.pic.p_fenc[1], FENC_STRIDE, 8 );
diff --git a/encoder/encoder.c b/encoder/encoder.c
index 3c95e8606..caefa669f 100644
--- a/encoder/encoder.c
+++ b/encoder/encoder.c
@@ -981,6 +981,7 @@ int x264_encoder_headers( x264_t *h, x264_nal_t **pp_nal, int *pi_nal )
         x264_nal_start( h, NAL_PPS, NAL_PRIORITY_HIGHEST );
         x264_pps_write( &h->out.bs, h->pps );
         x264_nal_end( h );
+        bs_flush( &h->out.bs );
     }
     /* now set output*/
     *pi_nal = h->out.i_nal;
@@ -1374,6 +1375,7 @@ static int x264_slice_write( x264_t *h )
             bs_write_ue( &h->out.bs, i_skip );  /* last skip run */
         /* rbsp_slice_trailing_bits */
         bs_rbsp_trailing( &h->out.bs );
+        bs_flush( &h->out.bs );
     }
 
     x264_nal_end( h );